Brain lesions in pigs dually infected with porcine reproductive and respiratory syndrome virus and pseudorabies virus

Four pigs were inoculated with an aerosol containing porcine reproductive and respiratory syndrome virus (PRRSV) followed 14 days later by inoculation with pseudorabies virus (PRV). The four dually infected pigs showed severe clinical signs, and one died on day 6 after infection with PRV. As demonstrated previously, the clinical disease was much more severe than that produced by either virus alone. All four dually infected pigs developed severe non-suppurative encephalitis, two had tonsillitis, two had necrotizing bronchiolitis, and one had lymphadenitis. The distribution of lesions corresponded closely with the detection of intranuclear inclusion bodies and PRV antigen. High numbers of TUNEL-positive cells detected in the thymus were associated with thymic atrophy.